In the space environment, it is of utmost importance that spacecraft components be deployed, moved, oriented and actuated in a reliable, fine-tuneable and fail-safe manner. Many spacecraft components, e.g., spacecraft booms, solar panels, antennas, payloads, instruments, sensors, satellite modules, separated hardware and star trackers, have parts which must be moved, either in a linear or pivoting manner with respect to other parts. In moving the parts with respect to one another, conventional, mechanical actuation is the current standard. However, it is desired to provide a more flexible and reliable operation in the space environment.
Micro-electrcomechanical systems (MEMS) have been proposed for propulsion systems that could be used to position or propel microsatellites for space, defense and communications applications, as well as for other uses.
The use of extremely small thrust impulse bits in packages of sub-millimeter length scales is under consideration for a wide variety of applications. The small size has so far made it desirable to keep the construction simple by producing only a simple burst disk nozzle opening. Upon opening a burst disk, the gas expels from the thrust chamber and produces an impulse. U.S. Pat. No. 6,131,385 referred to above discloses an integrated pulsed propulsion and structural support system for a microsatellite employing a microthruster capable of being fabricated by batch processing similar to integrated microelectronics.
Commonly assigned U.S. patent application Ser. No. 09/449,427 referred to above discloses an improved microthruster that will provide both higher thrust efficiency and more controllable and uniform impulse characteristics, and will make the magnitude of the impulse from microthrusters more uniform and controllable. That application discloses a microthruster, which comprises a closed chamber for carrying a fluid with a portion of the chamber less resistant to rupture from elevated fluid pressure than other portions of the chamber. The microthruster further includes an aerospike, which extends outwardly beyond the face of an outer wall of the closed chamber in the vicinity of the portion less resistant to rupture. It has been found that this microthruster improves the gas dynamics during propulsion for higher thrust efficiency and more controllable and uniform impulse characteristics. The microthruster is disclosed to be particularly useful as a propellant for a microsatellite.
According to the present invention, microthrusters, which have previously been proposed as a propulsion system for microsatellites, are used in spacecraft components to move parts of the spacecraft components with respect to one another. According to the present invention, the term xe2x80x9cspacecraft componentxe2x80x9d encompasses, but is not limited to spacecraft booms, solar panels, antennas, payloads, instruments, sensors, satellite modules, separated hardware and star trackers. Such components have a plurality of parts connected to one another, at least a first part being mounted with respect to another of the parts. According to the present invention, at least one microthruster is provided on a first part and comprises a chamber, fluid provided in the chamber and a diaphragm covering an opening in the chamber. An array of such microthrusters can be used to provide a reliable and fine-tuneable movement or actuation system.
The parts of the spacecraft components can be mounted for linear movement with respect to one another and/or can be mounted for a pivoting motion with respect to one another. The spacecraft component can have first, second and third parts, the first part being mounted for linear movement with respect to the second part, and the second part being mounted for pivoting movement about the third part. The pivoting movement can be in two orthogonal directions about the third part, thereby providing movement in three dimensions. In this case, a microthruster or a microthruster array would be provided on the second part to provide the pivoting movement and a microthruster or microthruster array provided on the first part to provide the linear movement.
The microthruster used in the present invention can be of the type described in U.S. Pat. No. 6,131,385 or in copending application Ser. No. 09/449,427, now U.S. Pat. No. 6,487,844.